Brake Disc (Rotor)

Raise and support the front of the vehicle on jackstands. Remove the front wheels.

Remove the caliper assembly; do not let the caliper assembly hang by the brake hose, instead support it with a piece of wire looped around the front spring or control arm.

Remove the retaining screw from the brake rotor and remove the rotor from the hub.

An impact driver, No. 3 phillips screwdriver bit, and a hammer may be needed to remove the retaining screw. It is fairly easy to destroy the screw slots using an ordinary phillips screwdriver to remove the tightly driven screw (see photo).

To install the disc, replace the disc on the hub, screw in the retaining screw and replace the caliper assembly.

Fig. Fig. 1: The (front) rotor as it appears upon removal of the wheel

Fig. Fig. 2: Tie the caliper up out of the way so its weight is not supported by the rubber brake hose

Fig. Fig. 3: A penetrating lubricant may be used to loosen the screw

Fig. Fig. 4: An impact driver with a No. 3 Phillips bit is the best way to remove the set screw

Fig. Fig. 5: Spray-type penetrating lubricant may help free the disc-use it minimally and be sure to not spray the brake pads

Fig. Fig. 6: A soft mallet may help free the disc, but if the disc does not come free in your hands at this point ...

Fig. Fig. 7: ... proper sized bolts can be alternately threaded into the disc holes in order to press the rotor off

Fig. Fig. 8: The hub as it appears upon removal of the brake disc

INSPECTION

See Figures 9 and 10

The brake disc develops circular scores after long or even short usage when there is frequent braking. Excessive scoring not only causes a squealing brake, but also shortens the service life of the brake pads. However, light scoring of the disc surface, not exceeding 0.0152 in. (0.38mm) in depth, will result from normal use and is not detrimental to brake operation.

Differences in the left and right disc surfaces can result in uneven braking.

Disc runout is the movement of the disc from side-to-side. Position a dial indicator in the middle of the pad wear area and turn the disc, while checking the indicator. If disc runout exceeds 0.004 in. (0.1mm), replace the disc.

Fig. Fig. 9: Checking the disc runout with a dial indicator

Fig. Fig. 10: Checking the disc parallelism with a micrometer

Disc parallelism is the measurement of variations in disc thickness at several locations on the disc circumference. To measure parallelism, place a mark on the disc and measure the disc thickness with a micrometer. Repeat this measurement at eight (8) equal increments on the circumference of the disc. If the measurements vary more than .0028 in. (0.07mm), replace the disc.

Only the outer portion of the disc can be checked while installed on the vehicle. If the installed parallelism check is within specifications, but you have reason to suspect that parallelism is the problem, remove the disc and repeat the check using the center of pad wear for a checking point.